In vitro experimental study demonstrates high azo dye biodegradation by Candida tropicalis under high salinity, suggesting its potential for treating hypersaline industrial wastewater.
Key Points
To optimize culture conditions and determine the biodegradation pathways and osmoregulatory mechanisms of a novel halotolerant yeast, Candida tropicalis ZQ, for decolorizing azo dyes under high-salinity conditions.
Isolated Candida tropicalis ZQ from marine sediment and optimized growth parameters (sucrose, nitrogen source, pH, temperature, agitation) using single-factor experiments.
Assayed decolorization kinetics of Acid Red 3 R across varying salt concentrations (up to 100.0 g/L NaCl), measured intracellular enzyme activities, and conducted acute toxicity assays on metabolites.
Performed integrative genomic and transcriptomic analyses to elucidate metabolic breakdown pathways and osmoregulatory response strategies.
Under optimized culture conditions, the strain achieved >96% decolorization of 1200.0 µmol/L Acid Red 3 R within 12 h and retained >97.0% decolorization within 32 h at 100.0 g/L NaCl.
Intracellular enzymes—including NADH-DCIP reductase, lignin peroxidase, manganese peroxidase, and laccase—drove dye degradation, resulting in a substantial reduction in metabolite acute toxicity.
Genomic and transcriptomic profiling revealed a multi-step degradation cascade alongside salt-tolerance strategies involving high-salt-in, compatible solute accumulation, ergosterol synthesis, and casein kinase II signaling.